Generally, a rotational cutter refers to a brush cutter, which comprises a work head for cutting shrubs, grass, etc. A traditional work head usually comprises an upper plate, a lower plate and a blade with approximately two to four posts uniformly arranged on the lower plate. The blade is attached to a post via a hole defined on the blade and rotatably connected with the post. A bolt is extended through a bolt hole defined in the upper plate and threadly coupled to the post to provide a fixed connection between the upper plate and the lower plate. The work head is driven by an output shaft of the brush cutter to rotate the work head causing the blade to extend outwardly from the blade-plate under a rotational centrifugal force to cut grass, shrubs, etc.
While cutting shrubs or grass, the blade may become worn and may need to be replaced. By analyzing the structures in the prior art, it has been realized that the upper plate must be removed from the lower plate if the blade needs to be replaced and the method of replacement is very complicated. Specifically, the bolt must be wrenched off with the help of an auxiliary means such as a screwdriver and because the space between the upper plate and the frame of the brush cutter is small, the motion required to wrench the bolt can be interfered with by the frame. As a result, the entire work head usually needs to be removed from the brush cutter first resulting in wasted time and manpower.